Morphology and ecology of the testate amoeba Arcella gibbosa Penard 1890 isolated
from different microbiotops was investigated. A detailed morphometric description of
Arcella gibbosa is presented. Size frequency distribution analysis indicates that A. gibbosa
is a size-monomorphic species. Shell diameter and shell height are the most stable
characters, whereas length of apertural collar is the most variable one. Moreover, collar
length has no significant correlations with other shell measurements. The main
characters determining the distinctions between populations are shell diameter and
shell height. These features are stable within a separate population and various in
different ones. Populations from one biotope are more similar than those from different
ones. There is no discreteness in distribution of the characters between the populations,
which demonstrates significant monomorphism and stability of this species. A. gibbosa
is a highly eurybiontic species, which may dwell in both acidic and toxic conditions, in
a great variety of microbiotopes.